Detector circuit, signal processing circuit, and measurement instrument
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Solution Overview
Problem
Measurement instruments struggle to distinguish between noise originating from the device under test and noise added by the measurement instrument, leading to unreliable noise measurement and inability to detect small signals below the instrument's intrinsic noise level, with existing reference measurements being time-consuming and unreliable.
Innovation Solution
A detector circuit that utilizes a first and second signal input to receive complex-valued measurement signals from the device under test, averaging these signals with their complex conjugates over a predetermined number of samples to reduce noise from sources other than the device under test, while preserving the ability to analyze its noise contribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference measurement is conducted without the device under test to determine and subtract additional noise, then the measurement precision is improved, but the measurement time increases and reliability decreases due to instrument behavior changes
Solution Approach 1:
The patent applies preliminary action by performing the noise measurement and characterization during the same measurement process rather than requiring a separate reference measurement. The detector circuit continuously characterizes the noise contribution of the device under test along with the signal, eliminating the need for a preliminary reference measurement without the device under test.
2Measurement precision
If a reference measurement is conducted without the device under test to determine and subtract additional noise, then the measurement precision is improved, but the reliability decreases due to different instrument behavior
Solution Approach 1:
The patent applies continuity of useful action by maintaining the measurement process continuously present, meaning the detector circuit operates throughout the entire measurement duration to characterize noise. This continuous operation ensures that the noise characterization reflects the actual instrument behavior during the measurement, rather than under different conditions as in separate reference measurements.
3Device complexity
If conventional detectors are used, then the measurement process is simple, but the ability to detect small signals below the intrinsic noise level is lost
Solution Approach 1:
The patent applies another dimension by transitioning from conventional scalar detection to complex-valued detection. The detector circuit processes signals in the complex domain, capturing both magnitude and phase information. This dimensional expansion enables the separation of signal components and noise through complex averaging, thereby detecting small signals that would be obscured in conventional real-valued detection.
Solution Approach 2:
The patent applies parameter changes by utilizing complex-valued measurement signals instead of conventional real-valued signals. By changing the mathematical domain from real to complex numbers, the detector circuit gains additional degrees of freedom for signal processing. This parameter change enables the implementation of complex averaging that effectively separates signal from noise, improving small signal detection capability.
Data Source
AI summary
A detector circuit for a measurement instrument is described. The detector circuit includes a first signal input, a second signal input, and an averaging sub-circuit. The first signal input is configured to receive a first complex-valued measurement signal associated with an input signal received from a device under test. The second signal input is configured to receive a second complex-valued measurement signal associated with the input signal received from the device under test. The averaging sub-circuit is configured to determine an average of the first complex-valued measurement signal and of a complex conjugate of the second complex-valued measurement signal over a predetermined number of samples, thereby obtaining a complex-valued average signal. The averaging sub-circuit is configured to generate an output signal based on the complex-valued average signal. Further, a signal processing circuit and a measurement instrument are described.